1. Field of the Invention
The present invention relates to a method for detecting an abnormality of temperature sensors with which an abnormality of the battery temperature sensors can be detected accurately, and to a power supply apparatus.
2. Description of the Background Art
Vehicles such as electric vehicles or hybrid vehicles that obtain the vehicle-drive power from a motor are equipped with a battery, that is, a secondary battery. The electric vehicles use the electric power stored in the secondary battery for rotating the motor so that the vehicles can travel. There are hybrid vehicles that use the electric power stored in the secondary battery for rotating the motor so that the vehicles can travel, and hybrid vehicles that use the engine as well as the motor so that the vehicles can travel.
The secondary battery mounted on the hybrid vehicle is a battery including an assembled battery in which a plurality of cells are arranged as a group. To the assembled battery, charging control has been provided by detecting SOC (State Of Charge) based on the voltage and current. Japanese Patent Laying-Open No. 2003-151643 discloses a technology for determining such a state of an assembled battery based on a current flowing through the assembled battery, voltages of a plurality of cells, and temperatures.
As above, among the hybrid vehicles, some employ the scheme for driving the wheels using both the drive power from the motor and the drive power from the engine. In this scheme, the charging/discharging amount that can be supplied to/from the battery is determined in accordance with the voltage, current and temperature of the battery. Based on the charging/discharging amount that can be supplied to/from the battery, the drive power sharing between the motor and the engine is controlled.
However, if measurement of the battery temperature is not accurately performed, there may be a case where control is provided in a state where the drive power share of the engine being greater than in the ideal drive power sharing. In such a state, the concentration of undesirable components such as nitrogen oxide is higher than in the ideal exhaust.
Such components are purified by the action of a catalyst provided in the exhaust path when the vehicle is normally traveling. However, in order for the catalyst to exert its effect of purifying the exhaust gas, the catalyst must be fully warmed. Therefore, the concentration tends to increase just after the start up of the engine, where the catalyst is not pre-heated.
Accordingly, in order to provide control of the hybrid vehicle with the ideal drive power sharing, it is desirable that an abnormality occurring with a temperature sensor is accurately detected so that the temperature sensor is repaired.
Conventionally, when monitoring the battery with a plurality of temperature sensors, a temperature sensor has been assumed to be abnormal when the temperature sensor indicates the measured temperature significantly different from those of the other temperature sensors.
On the other hand, when providing a temperature sensor for each of a plurality of cells included in the assembled battery, the temperature variation among the plurality of cells differs depending on the arrangement of the cells for each vehicle type, the performance of the cooling fan or the like. In addition, there may be a case where the temperature is actually different among the temperature sensors. Accordingly, it has been difficult to accurately detect an abnormality of the temperature sensors.